M. G. GEVORGYAN, G. A. PARSADANYAN and N. M. BEYLERIAN*
Department of Physical and Colloid Chemistry & Department of Ecology and Nature Conservation, Yerevan State University, 1 A. Manoogian St., Yerevan 375025, Armenia.
 

Abstract — Kinetics of sodium phenolphthalein phosphate enzyme catalyzed hydrolysis in leached soil, has been studied. It has been established that the action of the basic phosphatase of the soil may be explained by substrate inhibition mechanism. Kinetic and activation parameters of the reaction rate are determined. Determined in leached and carbonate chernozems phosphatase reaction parameters are compared.

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Abstract — Tweens, a group of non ionic surfactants, are commercially used for the preparation of micelles and reverse micelles. For useful applications in different fields, characterization of the Tweens is needed. This has been amply done by researchers in this field and can be found in literature. The useful physical parameters and characteristic features of Tween micelles are presented and discussed in this review.

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Abstract — Structure of the refolded β-lactoglobulin has been compared with that of native β-lac-toglobulin by measuring the accessibility of the various regions of the protein molecule. Site selective fluorescence labelling was employed to introduce fluorophores into various regions of β-lac-toglobulin and collisional quenching of intrinsic and labelled fluorophores was used to measure the Stern-Volmer quenching constant used here as a measure of the exposure or accessibility of the region. Our data indicate that tryptophan residues of the refolded β-lactoglobulin relocate from the central region towards the protein surface and this relocation helps to open up the access path to the central cavity. Measurement of kinetics of reaction of the free thiol group with DTNB reveals that in the refolded β-lactoglobulin most of the free thiols are involved in the interchange reaction with disulphides. Blocking of the thiol group with IAEDANS inhibits this interchange reaction. There is difference in quaternary structure between the native and the thermally refolded β-lac-toglobulin. On heating and subsequent cooling of β-lactoglobulin solution, much of the native
dimeric form dissociates into monomer and some minor fractions of the high molecular species of β-lactoglobulin were also observed.
 

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Abstract — In the original Tamele method (Amine titration method) n-butylamine has been used as a base (titrant) and benzene as a solvent. Since benzene is considered to be carcinogenic and nbutylamine is a toxic organic compound, attempt has been made to replace both of these two compounds for measuring the surface acidity of silica-alumina solid catalysts. For this purpose amorphous silica-alumina catalysts having three different silicon/aluminum ratios were prepared. Prior to carrying out the amine titrations, the solid catalyst samples were activated at 450ºC. In the titrimetric method benzene was replaced by cyclohexane, n-hexane and n-heptane and n-butylamine by di-n-butylamine. The parameters varied were concentration of di-n-butylamine solution, sample size of catalyst and type of catalyst smaples. It was observed that the total surface acidity of silica-alumina catalyst could be measured using a dilute solution of di-n-butylamine in cyclohexane or n-hexane or n-heptane. The total surface acidity of all the catalyst samples were found to be greater when cyclohexane was used as a solvent. A modified Tamele method has, therefore, been suggested replacing benzene with cyclohexane as the solvent and di-n-butylamine as the titrant.
 

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Abstract — Structural transitions in organized assemblies of a surfactant, Sodium Dodecyl Sulphate (SDS) in presence of additives, were studied by viscometric measurements under Newtonian flow conditions. Bromides of Li, Na, K, Rb and Cs were used as additives at various concentrations of SDS micellar solution. The dependence of the changes in viscosity on the added counter ion and its nature was studied at 30ºC. The competitive counter ion binding to SDS micelles was studied because it is a salt of a strong acid and cannot interact specifically through hydrogen bonds with adjacent water molecules. At 0.1 and 0.3 M SDS concentrations, more or less the same behaviour, i.e., a decrease followed by an increase in viscosity was observed, which was explained in terms of the balance of two opposing effects, the salt induced micellar growth and the transfer of the bound Na+ into the aqueous phase. The abrupt rise may be due to the samll ionization degree and small attractive energy contribution. In 0.5 M SDS solution, solubility of the salts are reduced which can force them towards the micelle-water interface and this promotes the transition.
 

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Abstract - Acrylonitrile has been graft co polymerized onto a starch-based biodegradable film. The characterization of the acrylonitrile grafted biodegradable film has been done by IR spectroscopy, XRD, SEM and thermal analysis. The evaluation of the film was made in terms of its thickness, density, water absorption, water vapor transmission, mechanical properties and biodegradability. Since grafting onto a polymer is mainly confined to the surface, the modification of polymer by grafting is more pronounced in the film form than any other form of the bulk polymer.
 

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RAM PARTAP^a*, NEELAM SWAROOP^b and D. K. TYAGI^c
aDepartment of Chemistry, FGM Government College, Adampur (Hisar) 125052, India
^bJain Kanya Pathshala P. G. College, Mujaffar Nagar (U.P.), India
^cDepartment of Chemistry, DAV College, Dehradun, India
 

Abstract - The surface tension for aqueous solution of AOT with/without NaCl have been measured at 288, 293 and 298 K. These data have been utilized for calculation of CMC, maximum surface excess concentration (Γ_max) and minimum area per molecule (A_min) of the surfactant at airliquid interface. Thermodynamic parameters of micellization and adsorption have been evaluated from CMC data. The micellization process is exothermic while adsorption is endothermic in nature.
 

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Abstract - Local anesthetics provoke reversible blockade of nerves by interaction with sodium channels in nerve membranes. On their route to the specific receptor sites, these molecules have to encounter the lipid bilayer. Effects of uncharged local anesthetics (LA) on a fully hydrated 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine (POPC) bilayer in liquid crystal phase have been investigated with molecular dynamics (MD) simulation scheme. Using two different LA molecules, Benzocaine (BZC) and Lidocaine (LDC), in low anesthetic concentration, comparisons have been made for their dynamical behavior in the membrane as well as their effect on membrane lipids. The differences in the mobility of the two anesthetics and the extent of increase of order in the interior of lipid bilayer have clearly been shown. The diffusion coefficient for two anesthetics in lipid environment was calculated which are comparable to experimentally determined values.
 

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Intramolecular Charge Transfer in Organized Assemblies : Fluorescence of 3-Acetyl-4-oxo-6, 7-dihydro-12H indolo-[2,3-a] quinolizine in Reverse Micelles

Abstract - Intramolecular charge transfer (ICT) fluorescence of a biologically active fluorophore, 3-acetyl-4-oxo-6,7-dihydro-12H indolo-[2,3-a] quinolizine (AODIQ) has been studied in reverse micelles formed by sodium bis(2-ethylhexyl)sulfo succinate (AOT) in heptane using steady state fluorescence, fluorescence anisotropy and picosecond time resolved fluorescence anisotropy. The charge transfer (CT) fluorescence exhibits appreciable red shift along with an enhancement of the fluorescence yield in the reverse micellar environment upon increasing water/surfactant mole ratio (W). This is associated with a sharp decrease in the fluorescence anisotropy (r), which suggests that the overall motional restriction experienced by the molecule is decreased with increased hydration. Metal induced fluorescence quenching study at different W has been exploited to determine the micellar aggregation number as a function of W.